The invention pertains to a vacuum coating system with a housing in which several processing stations are provided, at least one of which is equipped with a sputter cathode, the system also being provided with transport carts, each carrying at least one substrate holder in or parallel to the coating plane into which at least one substrate can be inserted, and which, in the area of the substrate, has an opening which exposes the area to be coated.
Vacuum coating systems of the type described above are known as in-line sputtering systems and are used in particular for the coating of glasses with indium-tin oxide (ITO), SiO.sub.2, or Ta.sub.2 O.sub.5 for display technology.
In known vacuum coating systems of a different design, sputter-etching is used to clean the substrates. In this case, it is not the cathode with the target but rather the electrically nonconductive substrate which is exposed to high-frequency energy. A plasma is thus formed at the substrate, and this plasma removes oxide layers and impurities from the surface. In the case of electrically conductive substrates, the substrate material is treated with high-frequency energy by applying the high frequency to the substrate holder, which is designed as an open frame. When the substrates are not electrically conductive, however, the substrate holders must have a closed surface behind the substrates, because otherwise no etching action would be achievable on the nonconductive substrates.
A closed surface of this type, however, cannot be realized when a substrate heater must be installed behind the substrates. A heater is advantageous, for example, when glasses are to be coated with indium-tin oxide by sputtering. This creates the dilemma that, for the process of sputter etching, the area behind the substrates must be closed, but for the process of heating the substrate during sputtering, this area must remain open.